Method and device for conveying particulate material during the layer-wise production of patterns

ABSTRACT

The present invention relates to apparatus, devices and methods for conveying particulate material during the manufacture of patterns in layers, wherein powder is conveyed out of a reservoir into a spreader unit and, if applicable, excess powder fed to the spreader unit is again conveyed back into the reservoir and wherein this conveying takes place in a closed conveying circuit.

CLAIM OF PRIORITY

This application is divisional patent of U.S. patent application Ser.No. 12/681,961 (filed Apr. 7, 2010), which is incorporated herein byreference in its entirety. U.S. patent application Ser. No. 12/681,961is a national phase of PCT application No. PCT/DE2008/001602, filed Oct.6, 2008, which claims priority to German Application No. DE 10 2007 050679.3, filed Oct. 21, 2007, all of which are incorporated herein byreference. This patent application claims priority to U.S. patentapplication Ser. No. 12/681,961, filed Apr. 7, 2010, PCT application No.PCT/DE2008/001602, filed Oct. 6, 2008, and German Application No. DE 102007 050 679.3, filed Oct. 21, 2007

FIELD OF THE INVENTION

The invention relates to a method and to a device for conveyingparticulate material during the manufacture of patterns in layers.

BACKGROUND

Methods for producing three-dimensional components have already beenknown for a long time.

European patent specification EP 0 431 924 B1, for example, describes amethod for producing three-dimensional objects from computer data. Aparticulate material is thereby applied onto a platform in a thin layerand said platform is selectively imprinted with a binder material bymeans of a print head. The particulate area, which is imprinted with thebinder, adheres and solidifies under the impact of the binder and anadditional hardener, if applicable. The platform is subsequently loweredby a layer thickness in a construction cylinder and is provided with anew layer of particulate material, which is also imprinted, as isdescribed above. These steps are repeated until a certain, desiredheight of the object is reached. A three-dimensional object is thuscreated from the imprinted and solidified areas.

After its completion, this object, which is produced from solidifiedparticulate material, is embedded in the loose particulate material andis subsequently freed therefrom. This takes place, for example, by meansof a vacuum cleaner. Thereafter, the desired objects, which are thenfreed from the residual powder, e.g., by means of brushing, remain.

Other powder-supported rapid-prototyping processes, such as theselective laser sintering or the electron beam sintering, e.g., in thecase of which a loose particulate material is also in each case appliedin layers and is selectively solidified by means of a controlledphysical source of radiation, also operate in a similar manner.

All of these methods will be combined herein below under the term“three-dimensional print processes”.

In the case of the three-dimensional print process known from the stateof the art, the particulate material is typically applied by means of aspreader unit. In the case of a low fill level, this spreader unit mustbe filled with particulate material from a reservoir.

Different methods and device are known from the state of the art forthis purpose.

WO 98/28124 A1, for instance, describes a method, in the case of whichthe powder material is pushed onto a workspace via a piston and isapplied from there via rollers onto the area, which is to be coated.

A device for filling a spreader device is further known from WO 00/78485A2, in the case of which a reservoir is arranged in an end position ofthe spreader device thereabove, with said reservoir encompassing asliding closure, wherein this sliding closure can be opened, if needed,and the spreader device can thus be filled.

A device, in the case of which the conveying of the particulate materialout of the reservoir into the spreader device takes place via a conveyorbelt, is furthermore known from the same patent application.

WO 2003/97518 further describes the conveying of the particulatematerial out of the reservoir into the speeder system via a slider.

A conveying device, which uses a belt transport system comprisingconveyor cages for transporting particulate material to the spreaderdevice, is further known from US 2004/0012112 A1.

A further possibility for conveying particulate material out of areservoir into a spreader system is described in DE 10 2005 056 260 A1.In the case of a low fill level, the spreader unit is hereby filled withparticulate material from a reservoir in such a manner that the filllevel in the spreader unit reaches a predetermined level across theentire length of the spreader device even in the case of a previouslyirregular fill level.

In the case of these methods and devices for filling a spreader unit forfluids, which are known from the state of the art, it has proven to bedisadvantageous that one fill level control is always necessary. Anuneven filling across the length of the spreader device can furthermoreonly be compensated or to an unsatisfactory degree with the methods fromthe state of the art.

SUMMARY OF THE INVENTION

It is thus the objective of the present invention to provide a methodand a device to refrain from using a fill level control and to evenlyfill the spreader device across the entire length.

This objective is solved by means of a method for conveying particulatematerial during the manufacture of patterns in layers, wherein powderfrom a reservoir is conveyed into a spreader unit and, if applicable,excess powder fed to the spreader unit is again conveyed back into thereservoir and wherein this conveying takes place in a closed conveyingcircuit.

In the case of such a method according to the invention, it is nowpossible for particulate material to be conveyed out of a reservoir intothe spreader system and for excess powder to again be conveyed back tothe reservoir by means of conveying the particular material in aconveying circuit.

The spreader system is thus filled until it is filled completely andexcess particulate material is again fed back directly to the reservoir.This means that the filling runs for a certain (reliable) period andthat one can be sure that the spreader device is filled completely. Inthe event that the spreader device is full, the excess particulatematerial is simply conveyed back to the reservoir.

Accordingly, pursuant to a first aspect of the present invention, thereis contemplated a method for conveying particulate material during themanufacture of patterns in layers, wherein powder is conveyed out of areservoir into a spreader unit and, if applicable, excess powder fed tothe spreader unit is again conveyed back into the reservoir and whereinthis conveying takes place in a closed conveying circuit.

The first aspect of the present invention may be further characterizedby one or any combination of the features described herein, such as thepowder conveying takes place via screw conveyors; the powder conveyingtakes place via low pressure; the powder conveying of the conveyingcircuit takes place via an individual conveying systems; the powderconveying of the conveying circuit takes place via a plurality ofconveying systems; the powder conveying of the conveying circuit takesplace via conveyor belts and/or conveyor cages; the powder conveying outof the reservoir into the spreader system takes place via an ejectionsystem; the conveying circuit conveys excess powder material back intothe reservoir after the coating process.

Accordingly, pursuant to a second aspect of the present invention, thereis contemplated a device for conveying particulate material during themanufacture of patterns in layers, encompassing a reservoir, a spreaderunit and a powder conveying system, wherein at least the reservoir andthe spreader unit are contained in a closed conveying circuit.

The second aspect of the present invention may be further characterizedby one or any combination of the features described herein, such asprovision is furthermore made for an ejection system; the reservoir isarranged below the spreader unit in vertical direction, thus viewed inthe direction at right angles to the coating direction, at least duringfilling process; the powder conveying system encompasses at least oneconveyor belt; the powder conveying system encompasses screw conveyors;the powder conveying system encompasses a suction device for lowpressure conveying; the ejection system encompasses two coverscomprising slits; the ejection system encompasses two tubes locatedwithin one another and comprising boreholes, which are arranged so as tobe offset; provision is furthermore made for a junction for introducingnew powder material into the reservoir.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a common method for applying particulate material inlayers;

FIG. 2 shows a device according to the invention according to apreferred embodiment;

FIG. 3 shows a device according to the invention according to a furtherpreferred embodiment;

FIG. 4 shows a particularly preferred embodiment of a conveying system;

FIG. 5 shows a further preferred embodiment of a conveying system;

FIG. 6 shows yet a further preferred embodiment of a conveying system;

FIG. 7 shows a preferred embodiment of the ejection system;

FIG. 8 shows a further preferred embodiment of the ejection systemaccording to the invention;

FIG. 9 shows yet a further preferred embodiment of the ejection system;

FIG. 10 shows a further preferred embodiment of a conveying system; and

FIG. 11 shows a refilling device according to a preferred embodiment ofthe invention.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, a closed conveying system thusrefers to a system, in the case of which a conveying to the spreaderdevice system takes place and from there also back into the reservoir,if applicable.

According to a preferred embodiment of the present invention, theconveying of powder could take place via screw conveyors.

Apart from this or in addition thereto, it would also be possible forthe conveying of powder to take place via low pressure.

A conveying via low pressure can be advantageous in particular when theconveying is to take place in a conveying system, which is closed offfrom the environment.

In the case of the method according to the invention, it can furthermorebe advantageous when the conveying of powder of the conveying circuittakes place via an individual conveying system. The different conveyingsystems must then possibly not be coordinated.

However, it is also possible for the conveying of powder of theconveying circuit to take place via a plurality of conveying systems inthe case of the method according to the invention.

The conveying of the particulate material out of the reservoir into thespreader system and back to the reservoir can take place via allpossible conceivable individual or a plurality of conveying methods inthe case of a method according to the invention. In addition to screwconveyors and low pressure, this could be conveyor belts and/or conveyorcages, for example.

According to the present invention, it can furthermore also beadvantageous when the conveying of powder out of the reservoir into thespreader system takes place via an ejection system.

Such an embodiment of the present invention has thus proven to beparticularly advantageous, because an even filling can take place in thespreader system due to the use of the ejection device.

According to a preferred embodiment it can be advantageous in the caseof the method according to the invention when the conveying circuit alsoconveys excess powder material back into the reservoir after thespreading process. If applicable, this excess particulate material fromthe coating method could also be cleaned before it is conveyed back tothe reservoir. A conveying could thus take place through a screen, forexample.

The objective of the present invention is further solved by means of adevice for conveying particulate material during manufacture of patternsin layers encompassing a reservoir, a spreader unit and a powderconveying system, wherein at least the reservoir and the spreader unitare contained in a closed conveying circuit.

According to a preferred embodiment of the device according to theinvention, provision is furthermore made for an ejection system. Such anejection system can be suitable to attain a particularly even leveldistribution of the particulate material in the spreader system.

It can be advantageous in particular with reference to the machinegeometry when the reservoir in the case of the device according to theinvention is arranged below the spreader unit in vertical direction,thus viewed in the direction at right angles to the coating direction,at least during a filling process.

It can furthermore be advantageous for the device according to theinvention when the powder conveying system encompasses at least oneconveyor belt.

In addition, it would also be possible, however, for the device as apowder conveying system to encompass screw conveyors and/or a suctiondevice for the low pressure conveying.

In the event that the device according to the invention encompasses anejection system according to a preferred embodiment, it may beadvantageous for the ejection system to encompass two covers comprisingslits.

In addition, it is also possible for the device to be provided in such amanner that the ejection system encompasses two tubes located within oneanother and comprising boreholes or slits, which are arranged so as tobe offset.

In the event a junction for introducing new powder material into thereservoir is provided according to the invention, the refilling ofparticulate material into the reservoir is possibly particularly simpleand clean.

To elaborate in more detail, the invention will be described in moredetail below by means of preferred exemplary embodiments with referenceto the drawing.

FIG. 1 generally describes a particulate coating process.

The method according to the invention and the device according to theinvention are to be explained in the following in an exemplary mannerfor the use during the assembling of casting patterns in layers fromparticulate material, binding material and hardener in the case of arapid-prototyping method.

In the case of an assembling method of a component, which is describedwith reference to FIG. 1, such as of a casting pattern, for example, abuild platform 9 on which the casting pattern is to be set up, islowered by a layer thickness of the particulate material 2. Particulatematerial 2 is subsequently applied from a spreader system 4 onto thebuild platform 9 in a desired layer thickness.

The selective application of hardener onto areas, which are to behardened, then takes place between the set-up of the individual layers.

At the onset of the coating process, the spreader system 4 is moved froma starting position across the workpiece platform. This is illustratedin FIG. 1a ).

The spreader system 4 now moves across the build platform 9 at aconstant speed. It thereby releases particulate material 2 in preciselythe correct quantity and creates thin layers 5 of the particulatematerial 2 on the build platform 9. This is shown in FIG. 1b ).

The spreader system 4 is subsequently moved back into the startingposition and can be newly filled from a particulate reservoir 1 via afilling device by opening the ejection slider 3. This is shown in FIG.1c ).

The filling of the spreader system 4 via a circuit system according tothe invention is illustrated in FIG. 2.

As can be seen from the figure, the particulate material 2 is conveyedout of a reservoir 17, which is located below the level of the movementplane of the spreader device and below the machine table 8, via a firstconveying system 12 to a level above the spreader device 4 for thispurpose. This means that the reservoir is arranged below the spreaderunit in vertical direction, thus viewed in the direction at right anglesto the coating direction at least during a filling process.

The particulate material according to the shown preferred embodiment isrealized via a shiftable ejection system 15 via a further conveyingsystem 13 (separately or part of the first system). Excess powder isguided back again into the reservoir or into the reservoir chamber 17,respectively, via a bypass system 16.

In the case of the illustrated preferred embodiment of the invention,the component parts of the device, comprising conveying devices 12, 13,reservoir 17, ejection system 15, bypass 16 and spreader device 4 arearranged in a vertical plane parallel to the spreader device in responseto the filling process. The advantage of this configuration lies in thatexcess powder or leakage can flow directly back into the reservoir.

FIG. 3 illustrated a further preferred embodiment of the invention. Ascan easily be seen in this figure, two openings 19, 18 are arranged inthe machine table 8 comprising the build platform 9. A first opening 16hereby serves for the powder return in the conveying circuit, in thecase of which particulate material is conveyed from the reservoir 17 tothe spreader device 4 and a second opening 19 for accommodating excessparticulate material 11 of the coating process. This powder can havebeen contaminated by the building process. It can thus be advantageousfor it to be discharged into a separate container. In addition, however,it could also be the case that it is directly subjected to a cleaning.

As is shown in FIG. 4, the conveying systems 12, 13 can be embodiedaccording to a preferred embodiment by means of screw conveyors 21,which are embodied in tubes. Likewise, however, it is also possible touse conveyor belts, conveyor belts comprising conveyor cages or vacuumdevices.

In the event that screw conveyors are used, it can be advantageous twoseparate systems 12, 13 are provided. A first screw conveyor takes overthe transport of the powder to a level above the spreader device 4.Curved or beveled systems provide advantageous powder absorption fromthe reservoir 17, are particularly suitable. A second screw conveyorruns horizontally above the spreader device 4. It takes over thetransport to the spreader device 4 and to the bypass 16.

For filling, the spreader device 4 moves into a position below thefilling system. The coating reservoir is thereby preferably embodied ina funnel-shaped manner. As is illustrated in FIG. 3, only a narrow gapis located in the position between spreader device 4 and ejection system15.

An ejection system 15 according to the present invention can be operatedin all conceivable manners. As an example, two different systems are tobe described herein with reference to FIGS. 4, 5 and 6.

For example, an ejection device 15 can be opened according to a method,which is known from the state of the art, in response to a filledtransport system and the available powder can thus be shaken off. Theconveying device is thereby not active. In the case of this method, adefined powder quantity is refilled into the spreader device. This isillustrated in FIG. 7 using reference numeral 20. Level differenceswithin the spreader device, which are created during the buildingprocess, can only be compensated to a limited extent in the case of thistype of operation. Such a filling is called impact filling.

According to a preferred embodiment of the present invention, thespreader device can be filled in that the ejection device 15 is openedand the conveying system 12, 13 is activated. As is illustrated in FIG.5, the spreader device 4 is filled with particulate material 2 intransport direction of the transport device. In the case of an excessivefilling time, excess powder falls past the spreader device 4 and backinto the reservoir 6. This is illustrated in FIG. 6 by means ofreference numeral 24. It would furthermore also be possible for theexcess powder to be fed back to the powder circuit via the bypassopening 16. This is illustrated by means of reference numeral 22 in FIG.5. Such a filling is called level filling.

An advantage of such a level filling is that, in connection with thecircuit system, the filling can take place without a sensor. Due to thefact that a resupply can on principle take place without anydisadvantages for any amount of time in the case of a completely filledspreader device, no particular actions must be taken to protect allinvolved aggregates. The fill level can be secured via a simplepreselection of the filling period.

A further advantage lies in the even filling across the length of thespreader device.

In many cases, the fill level can change across the length during thebuilding process due to uneven powder outflow out of the spreaderdevice. An even refilling can be guaranteed in the case of eachrefilling by means of the level filling.

According to a preferred embodiment of the invention shown in FIG. 7,the ejection device is embodied as a cover system. In the case of suchan embodiment, two thin disks 25, 26 comprising boreholes 29 or slitsare used in the ejection system. The hole pattern of the one diskcorresponds to the second hole pattern, but is shifted to one another.Powder can escape 28 in the event that the disks are moved against oneanother 27 so that the hole patterns coincide. Gravity forces it to flowinto the spreader device.

The embodiment of such a system can be as a rectangular tube, forexample, wherein the underside encompasses a hole pattern. An additionaldisplaceable disk comprising a hole pattern completes the system.

An embodiment of the ejection system, in the case of which the describedhole patterns are realized on two tubes 31, 32, which run into oneanother, is particularly preferred. Such an embodiment can be seen inFIG. 8. In the case of this system, the opening for the powder dischargeis attained by means of rotating the tubes against one another. Theinner tube 31 encompasses a row of boreholes 29A at the lowermostlocation. The system is open in the event that the row of boreholes 29Bof the outer tube 32 is also brought into this position.

A tube cover system comprising a screw conveyor 21 in the interior isfurthermore particularly preferred. The above-described level fillingcan be realized in a particularly advantageous manner by means of such asystem.

The afore-described systems can be activated in different manners.According to a preferred embodiment, pneumatic electromagnetic andhydraulic actuators 33 are suitable. See FIG. 9.

In addition, provision can be made in the powder circuit for aconnection for fresh powder. This is illustrated in FIG. 10. Such afresh powder connection 14 is advantageously connected to one of thealready necessary conveying systems 12, 13.

The advantage as compared to the simple refilling into the reservoir 6lies in the constructively possible lower dust exposure for the user.

A system, in the case of which closed powder kegs 36 are placed onto aconnecting spigot comprising a funnel tube 14 and supply the system withfresh powder is particularly preferred.

As is illustrated in FIG. 11 in an exemplary manner, the kegs can beprovided with a membrane 38, which is opened only when placed onto thefunnel 37. Plastic, metal or paper are suitable as membrane substances.

The method according to the invention thus uses a powder circuit forfilling purposes, which makes it possible to fulfill the posed demands.Powder loss can be avoided by means of the embodiment of the powderconveyance in a circuit-like manner. A return of excess powder makes itpossible to fill the spreader device carriage at high speed to an evenlevel. A refilling device, which provides for a low-dust refilling, canbe used at the circuit. On the one hand, this benefits the safety andthe comfort of the user and, on the other hand, the explosion protectionrequirements.

What is claimed is:
 1. An apparatus for the manufacture of a threedimensional object in layers comprising i) a device for conveying aparticulate material during the manufacture of the object in layers,wherein the devise comprises a) a reservoir, b) a spreader unit, and c)a plurality of particulate material conveying systems including a firstparticulate material conveying system and a second particulate materialconveying system; and ii) a build platform on which the object is built;wherein the first particulate material conveying system conveys theparticulate material from the reservoir to the spreader; the spreader isadapted for being filled with the particulate material, releasing theparticulate material while moving over the build platform, and spreadingthe particulate material over the build platform; and the secondparticulate material conveying system conveys excess particulatematerial that was fed to the spreader back to the reservoir; so that atleast the reservoir and the spreader unit are contained in a closedconveying circuit.
 2. The apparatus according to claim 1, whereinprovision is furthermore made for an ejection system.
 3. The apparatusaccording to claim 1, wherein the reservoir is arranged below thespreader unit in a vertical at least during a filling process.
 4. Theapparatus according to claim 1, wherein the particulate materialconveying system comprises at least one conveyor belt.
 5. The apparatusaccording to claim 1, wherein the particulate material conveying systemcomprises screw conveyors.
 6. The apparatus according to claim 1,wherein the particulate material conveying system comprises a suctiondevice for low pressure conveying.
 7. The apparatus according to claim 2wherein the ejection system comprises two covers comprising slits. 8.The apparatus according to claim 2 wherein the ejection system comprisestwo tubes located within one another and comprising boreholes, which arearranged so as to be offset.
 9. The apparatus according to claim 1,wherein a provision is furthermore made for a junction for introducing anew particulate material into the reservoir.
 10. The apparatus accordingto claim 1, wherein the reservoir is maintained in a fixed position andthe spreader unit is movable relative to the reservoir.
 11. Theapparatus according to claim 1, wherein the build platform is movable inthe vertical direction.
 12. An apparatus for the manufacture of a threedimensional object in layers comprising i) a first device for conveyinga particulate material during the manufacture of the object in layers,wherein the devise comprises a) a reservoir, b) a spreader unit, and c)a plurality of particulate material conveying systems including a firstparticulate material conveying system and a second particulate materialconveying system, wherein the particulate material conveying systemcomprises screw conveyors; and ii) a build platform on which the objectis built; the first device includes a junction for introducing newparticulate material into the reservoir; the first particulate materialconveying system conveys the particulate material from the reservoir tothe spreader; the spreader is adapted for carrying the particulatematerial, releasing the particulate material while moving over the buildplatform, and spreading the particulate material onto the buildplatform; and the second particulate material conveying system conveysexcess particulate material that was fed to the spreader back to thereservoir; so that at least the reservoir and the spreader unit arecontained in a closed conveying circuit.
 13. The apparatus according toclaim 12, wherein the reservoir is maintained in a fixed position andthe spreader unit is movable relative to the reservoir; and the buildplatform is movable in the vertical direction.
 14. An apparatus for themanufacture of a three dimensional object in layers comprising i) afirst device for conveying a particulate material during the manufactureof the object in layers, wherein the devise comprises a) a reservoir, b)a spreader unit, and c) a plurality of particulate material conveyingsystems including a first particulate material conveying system and asecond particulate material conveying system, wherein the particulatematerial conveying systems comprises at least one conveyor belt; ii) abuild platform on which the object is built the first device includes ajunction for introducing new particulate material into the reservoir;the first particulate material conveying system conveys the particulatematerial from the reservoir to the spreader; the spreader is adapted forbeing filled with the particulate material, releasing the particulatematerial while moving over the build platform, and spreading theparticulate material onto the build platform; and the second particulatematerial conveying system conveys excess particulate material that wasfed to the spreader back to the reservoir; so that at least thereservoir and the spreader unit are contained in a closed conveyingcircuit.
 15. The apparatus according to claim 14, wherein the reservoiris maintained in a fixed position and the spreader unit is movablerelative to the reservoir; and the build platform is movable in thevertical direction.
 16. The apparatus of claims 1, wherein the buildplatform is movable in the vertical direction by a layer thickness ofone of the layers.
 17. The apparatus of claim 16, wherein the apparatusincludes an ejection system for evenly refilling the spreader unit withthe particulate material.
 18. The apparatus of claim 17, wherein theejection system includes a pair of tubes that rotate against one anothertwo provide an opening for discharge of the particulate material intothe spreader unit.
 19. The apparatus of claim 16, wherein the reservoiris maintained in a fixed position and the spreader unit is movablerelative to the reservoir.
 20. The apparatus of claim 16, wherein theapparatus includes an opening for removing the particulate material fromthe apparatus.
 21. The apparatus of claim 16, wherein the apparatusincludes an opening for recovering excess particulate material during afilling of spreader unit.